Leaderboard

Hi Bob, Hope your well, can't remember if I ever got to the bottom of it, I'll blow the dust off my notes next week and have a look.

Hi chaps, Here's a tricky one. All you Black Box owners are aware of the battery backed RAM board that has to be fitted for certain games to work. Well reading some documentation there used to be a chip in position IC8 socket where the fly lead for the RAM board plugs in. This was a RAM chip which has the designation 9410? In the loading diagram for the board it's listed as 9410B. I've searched the internet high and low and I can't find anything that matches. The pin out is somewhat unusual as can be seen by the power pins on the diagram below. The chip that was fitted on the RAM board was a 74C910 which has a totally different pin out. This was a 64 word x 4 bit RAM. Anyone come across this chip in their travels or even know what it's full number might be? I'm also curious as to why the original RAM chip was used as it wouldn't have had battery backup! I was thinking of perhaps using any old 2114 chip on a daughterboard just for testing purposes but I haven't a clue what pins 5(VGG) and 6(EXT) are for although from what I can make out from the diagram it's a -12v feed???.

OK, this is not unexpected when tracing faults on this board. You need to understand how the RESET circuit works otherwise nothing will make any sense. You won't need a scope at this point (probably later though). A quick overview.... all the supplies are monitored via diodes feeding in to TR10 and/or TR8. You have to find which supply(s) failures are getting through the diodes to cause the RESET to occur. 1st to check is IC2(8212) as this often fails, they aren't cheap either! With these boards I usually change all the transistors TR 8, 9, 10, 11, 12, 47, 48 and some others but more on that when you get it out of RESET. I can't emphasise enough the pins in the PSU socket, if these are contaminated you'll be getting RESET's intermittently all the time!!